A map which forwards all its method calls to another map. Subclasses should
override one or more methods to modify the behavior of the backing map as
desired per the decorator pattern.

Warning: The methods of ForwardingMap forward
indiscriminately to the methods of the delegate. For example,
overriding put(java.lang.Object,java.lang.Object) alone will not change the behavior of putAll(java.util.Map), which can lead to unexpected behavior. In this case, you should
override putAll as well, either providing your own implementation, or
delegating to the provided standardPutAll method.